<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    li {
      height: 30px;
      border: 1px solid orange;
    }
  </style>
</head>

<body>
  <ul>
    <li class="item">第1个</li>
    <li class="item">第2个</li>
    <li class="item">第3个</li>
    <li class="item">第4个</li>
    <li class="item">第5个</li>
    <li class="item">第6个</li>
  </ul>
  <script>
    var list = document.querySelectorAll(".item")
    for (var i = 0; i < list.length; i++) {
      list[i].addEventListener("click", function () {
        console.log(this);
        setInterval(() => {
          console.log('定时器');
          console.log(this);//this指向事件源对象
        }, 1000)
      })

    }

  </script>
</body>

</html>